RAGE to have 8GB install for PS3, and 3 discs on 360.

[Nsanity]

You can go anywhere no matter in wich disk you are. It seems that there is a Multiplayer disk and 2 for the campaign, also there is no swapping if you want to go back.

http://www.eurogamer.net/articles/digitalfoundry-the-return-of-id-software